The overall goal of this research is the design, development and in vivo testing of a biologically active, collagen-based coil for the embolization of cerebral aneurysms. Our research hypothesis for this investigation is that type I collagen-based material will promote and facilitate fibrous tissue formation within the aneurysm cavity and therefore, will stabilize the aneurysm for effective aneurysm occlusion. The hypothesis is based on numerous previous studies that collagen surface enhances cell adhesion, proliferation and extracellular cellular matrix synthesis, all of which contribute to fibrogenesis and fibrous tissue deposition, resulting in stable aneurysm occlusion. In phase I, we have developed a collagen-based coil prototype and tested the prototypes in vitro and in vivo in a rabbit saccular aneurysm model. Results of the in vivo studies demonstrated the feasibility of embolizing saccular aneurysms using coils constructed from purified type I collagen. However, several areas require improvement before the collagen-based coil can be used clinically. The coil must be deliverable, detachable, visible in vivo and retrievable. These improvements will be the subject of this phase II proposal.